Refrigeration compressor



1966 R. E. coMsTocK ETAL 3,233,322

REFRIGERATION COMPRESSOR Filed April 22, 1963 2 Sheets-Sheet 1 54 W j V I M INVENTORvfi. FzAstsur/f 2. Cams/ac United States Patent 3,233,822 REFRIGERAT 0N COMPRESSOR Russell E. Cornstock and Edwin L. Gannaway, Sidney, Ohio, assignors to Copeland Refrigeration Corporation, Sidney, Ohio, a corporation of Michigan Filed Apr. 22, 1963, Ser. No. 274,597 7 Claims. (Cl. 230-17) This invention relates to refrigeration compressors, and more particularly to systems for controlling the discharge pressure of such compressors.

Modern refrigeration design practice has required to a greater extent the use of hermetic compressor motors having sufficient torque capabilities to allow the refrigeration system to operate through severe maximum load conditions and with a wide range of voltage variation without the likelihood of nuisance protector trips. The use of such motors, however, may subject refrigeration systems, especially certain types of air conditioning units, to extremely high discharge pressures if the condensing means fails due to any of various reasons, such as electrical or mechanical fan failure, condenser blockage, air restriction or recirculation. Such high pressures, on the other hand, must be avoided in view of safety requirements imposed by industry standards. One industrial standards group, for example, requires that the pressure in a refrigerating system not exceed one-third of their hydrostatic test rating for the high pressure side components.

In attempting to comply with the above loading requirements while still providing protection against excessive discharge pressure, some compressor manufacturers have installed high pressure-responsive electrical cutout switches in addition to the usual protectors which are sensitive both to high current conditions and to motor winding or housing temperatures. However, such installations have been unsatisfactory from a cost standpoint and also due to the possibility of electrical malfunction of the high pressure control.

Many manufacturers utilize a relatively weak compressor motor which will stall upon heavy loading of the compressor, resulting in a high current which will trip the electrical protector. Alternatively, the electrical protector may be made sufficiently sensitive to heat or current as to open the motor circuit upon a moderate rise in discharge pressure. However, these expedients have the disadvantage of sacrificing the maximum load capabilities of the unit. Moreover, the last-mentioned alternative could not be used in the case of more powerful motors used with compressors having large displacements with respect to their condensers, since in the latter case the pressure would rise beyond the acceptable limit before the temperature increase trips the protector.

It is an object of the present invention to overcome the above-described disadvantages of known systems and to provide a novel and improved refrigeration compressor control system which will prevent excessive high side pressures but which at the same time is economical to install and reliable in operation.

It is another object to provide an improved refrigera tion compressor control of the above nature which is completely tamper proof in operation, is protected from mechanical damage, and will not interfere with the compressor complying with maximum load conditions.

Other objects, features, and advantages of the present invention will become apparent from the subsequent description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a cross-sectional view in elevation taken along the line 1--1 of FIGURE 2, and showing the manner in which the pressure limiting mechanism of this invention will coact with internal and external types of motor protectors, the pressure limiting mechanism being shown in phantom lines;

FIGURE 2 is a top plan view of the motor-compressor with the upper portion of the housing broken away and showing the mounting position of the pressure limiting mechanism;

FIGURE 3 is an elevational view taken in the directionof arrow 3 of FIGURE 1, parts being sectioned or broken away, and showing further details of the invention;

FIGURE 4 is a fragmentary side elevational view taken in the direction of the arrow 4 of FIGURE 2, parts being ectioned or broken away; and showing the mounting position of the pressure limiting valve;

FIGURE 5 is an enlarged elevational view in cross section showing the internal construction of the pressure limiting mechanism;

FIGURE 6 is a circuit diagram of the motor circuit showing the location of an external motor protector acted upon by the pressure limiting means of this invention; and

FIGURE 7 is a schematic diagram showing an arrangement for testing the operation of the invention.

In general terms, the illustrated embodiment of the invention comprises a pressure limiting mechanism in the form of a one-way valve connected between a mnfiler chamber at the discharge side of a hermetic compressor and the shell chamber which is connected with the suc: tion side of the compressor, the shell being provided with a conventional type of protector which will open the motor circuit in response to excessive current or shell temperature.

Normally, the pressure limiting mechanism will remain closed. However, should the pressure differential between the discharge and suction sides increase to a predetermined amount, below that which would be caused by a rise of discharge pressure above the permissible level,

the valve will open, bypassing the discharge gases to the shell chamber.

The pressure limiting device is so located with respect to the electrical protector that the hot discharge gases released therethrough will impinge upon the shell area in the immediate vicinity of the protector, thus rapidly raising the protector temperature to the point at which it will open the motor circuit. If the motor is provided with an internal type of protector which senses motor winding temperature directly, the hot bypassed discharge gases will rapidly heat this protector in a. similar manner and with the same result.

The pressure limiting device is adapted to close when the pressure differential between the discharge and suction sides drops somewhat from the openingpressure differential. In the case of some compressors, particularly smaller models, the pressure limiting valve will open and close several times before the protector is heated to the tripping point, the gauge pressure on both the suction and discharge sides building up gradually during this time. However, the gauge pressure at the discharge side when the compressor is shut off by the protector will still be below the maximum permissible pressure. In the case of-larger compressors, the valve may remain open continuously until the motor tn'ps out. Of course, if the cause of the discharge pressure buildup, such as a fan blockage, is corrected before the protector trips, the system will again function normally. After the protector has tripped, the unit will be disenabled until the protector cools and recloses in the usual manner. If the cause of high pressure has not been corrected, the cycle will then be repeated, but at no time will the discharge pressure be permitted to exceed the maximum permissible limit.

Because of the presence of the control system of this invention, the compressor motor may be made of sufficient strength to handle temporarily severe maximum load conditions, and the electrical protector need not have the high sensitivity which might otherwise be required and which could cause the motor to trip out upon encountering these temporary conditions.

I Referring more particularly to the drawings, the hermetic motor-compressor unit is generally indicated at 11 and comprises a shell generally indicated at 12 having an elliptical cross-sectional shape as seen in FIGURE 2, with the axis of the shell normally being vertical. Shell 12 is fabricated of a lower shell section 13 and an upper shell section 14 which are welded together at 15. An electric motor generally indicated at 16 and a compressor generally indicated at 17 are disposed within shell 12. Compressor 17 is axially aligned with motor 16 and is disposed therebelow, the compressor having a cylinder casting 18 with a compressor piston 19 mounted therein. Casting 18 supports a crankshaft 21 to which piston 19 is connected by a'connecting rod 22, and crankshaft 21 is connected to a rotor shaft 23 which extends upwardly through rotor 24 of motor 16.

The means for supporting motor 16 and compressor 17 comprises a helical compression spring 25 disposed between a downwardly extending bell-shaped member 26 attached to the top of shell section 14 and a circular supporting bracket 27 secured by bolts 28 to stator 29 of motor 16. More particularly, the inner flange 31 of annular member 27 rests on top of spring 25, the lower end of this spring being supported by the outer flange 32 of member 26. Additional lateral supporting means for motor 16 and compressor 17 is provided by a plurality of coil springs 33 which connect the underside of casting 18 with posts 34 fixed to brackets 35 within lower shell section 13. The motor-compressor supporting means does not in itself form part of the present invention.

Chamber 36 formed by shell 12 is adapted to be connected to that side of a refrigeration system which furnishes the suction gases to compressor 17; such a connection is indicated at 37 in FIGURE 2. A pair of vertically disposed tubes 38 and 39 connect chamber 36 with inlet chamber 41 of compressor 17, seen in FIG- URE 4. An inlet flapper valve 42 controls admission of suction gases to cylinder 43 of casting 18, and a discharge valve .44 controls the exit of discharge gases from cylinder 43 to the first chamber 45 of a mufiler 46 secured to the head of casting 18.

The configuration of mufiler 46 is seen best in FIG- URES 1 and 3, the muffler comprising a first chamber 45 and a second chamber 47 connected by a tube 48 extending on opposite sides of a wall 49 which separates chambers 45 and 47. A mufller cap 51 is secured to the upper end of muffler 46, and a discharge tube 52 is connected to cap 51 and extends downwardly through shell chamber 36 for connection to the high pressure side of the refrigerating system.

Shell 12 is being shown as being provided with an external electrical protector 53. This protector is of a conventional bimetal type and is mounted on portion 54 of upper shell section 14, immediately above the upper end of mufiler 46. Since protector 53 is of a conventional type, its mechanism need not be described in detail. However, it should be pointed out that, as shown in FIGURE 6, protector 53 is connected in series with the supply circuit 55 for rotor 24 and stator 29 of motor 16, and is responsive to prolonged excessive current in circuit 55 to move to a tripped or open position, cutting off the power supply to motor 16. At the same time, the mounting of protector 53 on shell 12 will cause the protector to trip in response to the attainment of the predetermined shell temperature, thus again opening the motor circuit. In other words, the protector operates in response to the combined effects of motor current and shell temperature.

Instead of external protector 53, unit 11 could be provided with an internal type of protector 53 which is mounted in direct heat-conductive relation with stator 16. In accordance with the invention, a pressure limiting valve generally indicated at 56 is mounted on the top of muffler 46 adjacent mufiler cap 51. The internal construction of valve 56 is best seen in FIGURE 5, the valve comprising a body 57 of elongated shape having a lower threaded end 58 mounted within the top of muffler 46, with an inlet port 59 connected with second muffler chamber 47. A valve seat 61 is formed at the upper end of port 59, and a spherical valve member 62 is disposed within body 57 and urged against seat 61 by a helical coil compression spring 63. A cover 64 is secured in the top of body 57 and supports the upper end of spring 63. An outlet port 65 is provided in cover 64, and two radially extending outlet ports 66 are provided in the upper portion of body 57 so that mufller chamber 47 will be connected to suction chamber 36 when valve member 62 is lifted from valve seat 61.

Valve 56 is so constructed as to remain closed as long as the pressure diffential between second mufiler chamber 47 and suction chamber 36 is less than a predetermined amount. However, when the pressure differential exceeds this amount, valve member 62 will be lifted from valve seat 61, permitting flow of the gases discharged from compressor 17 to suction chamber 36. The percentage of the total amount of gases discharged by compressor 17 which is bypassed through valve 56 will depend upon several factors, such as the relationship between the sizes of the compressor and condenser and the relationship of the sizes of ports 59, 65 and 66 to the compressor capacity. In any case, the inherent condensing action which will still take place in a condenser even if there is a fan blockage or similar malfunction would mean that under normal circumstances, even with valve 56 open, not quite all of the gases discharged by compressor 17 will be bypassed.

Because of the construction of valve 56, and the fact that the gases coming from mufller chamber 47 will act upon a larger effective area of valve member 62 after this member has been lifted from valve seat 61, valve 56 will not reclose until the pressure differential between chambers 47 and 36 drops to something less than that required to open the valve. In a typical installation, if valve 56 is set to open upon the pressure differential exceeding 550 p.s.i., it will close when the pressure differential drops below about 400 p.s.i.

Valve 56 is disposed directly below portion 54 of upper shell section 14 which supports protector 53. The discharge gases issuing from ports 65 and 66, and especially those released from port 65, will impinge upon portion 54 of shell section 14, thus tending to rapidly heat protector 53; these gases are indicated at 67 in FIGURE 1. Moreover, the bypassed gases will raise the temperature of the entire suction chamber 36, and some of them will be carried around to the other side of stator 29, as indicated by the reference numeral 68, and heat an internal protector 53' should one by mounted on the stator windings in this area.

It should be noted that, since the inlet port 59 for valve 56 is connected to a relatively large volume, namely, second muffler chamber 47, the release of pressure from this chamber through valve 56 will not drop the pressure in chamber 47 as rapidly as would be the case if port 59 were connected to tube 52 or some other chamber having relatively small volume. A rapid pressure drop at inlet port 59 after valve 56 opens might result in a chattering effect on valve member 62.

The operation of the invention may perhaps best be understood with reference to FIGURE 7, which is a schematic diagram showing an arrangement for testing a refrigerating system incorporating the principles of this invention. Normally, the refrigerant will flow from compressor 17 to condenser 69, evaporator 71 and back to compressor shell 12. Valve 56 will be closed at this time. The head pressure, as indicated by a gauge 72, will be about 280 p.s.i.g, and the suction pressure, as, indicated by a gauge 73, will be about 50 p.s.i.g.

When condenser fan 74 was stopped, the following sequence of pressures was recorded, the first group being recorded at 15 second intervals.

Suction Time Head Pres- 5 Seconds sure, p.s.i.g. Pressure, Remarks p.s.1.g.

Conditions when Ian was stopped.

Valve opened. Valve closed. Valve opened. Valve closed. Valve opened. Valve closed. Protector tripped.

-Upon closing of valve 56, the pressure differential again built up and the valve opened and closed repeatedly, both head pressure and suction pressure building up above the previous level upon each opening and closing portion of the cycle. The discharge gases impinging upon shell portion 54 in the vicinity of protector 53, and carried through the remainder of the chamber 36, served to heat protector 53 until, when the head pressure had reached 680 p.s.i.g., protector 53 tripped, stopping motor 16. The maximum head pressure reached, 680 p.s.i.g., was below the maximum permissible limit for the high side of the system as set by the industry standards under consideration.

While it will be apparent that the preferred embodiment of the invention disclosed is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. In combination, a refrigerant compressor, an electric motor for driving said compressor, a supply circuit for said motor, an electrical protector in said supply circuit and adapted to open said supply circuit in response to excessive heat or temperature, a suction chamber connected to the inlet side of said compressor and in heatconductive relation with said protector, a discharge cham- 55 ber connected to the outlet side of said compressor, and a normally closed valve connecting said chambers and adapted to open in response to the attainment of a predetermined pressure diiferential between said chambers to permit flow from said discharge to said suction chamher, whereby heat carried by the discharge gases passing through said valve will act upon said protector.

2. In a hermetic refrigerant motor-compressor unit of the type having a motor, a compressor, a shell surrounding said motor and compressor and forming a suction chamber connected to the inlet side of said compressor, and a discharge chamber connected to the outlet side of said compressor, an electrical protector connected to said motor and said shell and adapted to disenable said motor in response to excessive motor current or shell temperature and a normally closed valve connecting said discharge and suction chambers, said valve being adapted to open in response to the attainment of a first predetermined amount of pressure differential between said chambers so as to bypass discharge gases to the suction chamber with heat carried by said bypassed gases directly affecting said protector.

3. In a hermetic refrigerant motor-compressor unit of the type having a motor, a compressor, a shell surrounding said motor and compressor and forming a suction chamber connected to the inlet side of said compressor, and a discharge chamber connected to the outlet side of said compressor, an electrical protector connected to said motor and said shell and adapted to disenable said motor in response to excessive motor current or shell temperature, and a normally closed valve connecting said discharge and suction chambers, said valve being adapted to open in response to the attainment of a first predetermined amount of pressure differential between said chambers so as to bypass discharge gases to the suction chamber with heat carried by said bypassed gases directly affecting said protector, said valve being adapted to reclose when said pressure differential is reduced to a second predetermined amount below said first predetermined amount.

4. The combination according to claim 3, said valve comprising a body having an inlet port connected to said discharge chamber and at least one outlet port connected to said suction chamber, a valve seat between said ports, a valve member having a first effective area exposed to said inlet port when said valve member engages said valve seat and a second and larger effective area exposed to said inlet port when said valve member is lifted from said valve seat, and a spring urging said valve member against said valve seat.

5. In a hermetic refrigerant motor-compressor unit of the type having a motor, a compressor, a shell surrounding said motor and compressor and forming a suction chamber connected to the inlet side of said compressor, and a muffler having a discharge chamber connected to the outlet side of said compressor, an external type electrical protector mounted on said shell adjacent said mufiler and adapted to disenable said motor in response to excessive motor current or shell temperature, and a normally closed valve connecting said discharge and suction chambers, said valve being adapted to open in response to the attainment of a first predetermined amount of pressure differential between said chambers so as to bypass discharge gases to the suction chamber with heat carried by said bypassed gases directly affecting said protector.

6. In a hermetic refrigerant motor-compressor unit of the type having a motor, a compressor, a shell surrounding said motor and compressor and forming suction chamber connected to the inlet side of said compressor, and a muffler having a discharge chamber connected to the outlet side of said compressor, an external type electrical protector mounted on said shell adjacent said muffler and adapted to disenable said motor in response to excessive motor current or shell temperature, and a normally closed valve connecting said discharge and suction chambers, said valve being adapted to open in response to the attainment of a first predetermined amount of pressure differential between said chambers so as to bypass discharge gases to the suction chamber with heat carried by said bypassed gases directly affecting said protector, said valve comprising a body having an inlet port connected to said discharge chamber and at least one outlet port connected to said suction chamber, a valve seat between said ports, a valve member having a first effective area exposed to said inlet port when said valve member engages said valve seat and a second and larger effective area exposed to said inlet port when said valve member is lifted from said valve seat, and a spring urging said valve member against said valve seat.

7. In a hermetic refrigerant motor-compressor unit of the type having a motor with a rotor and stator, a compressor, a shell surrounding said motor and compressor and forming a suction chamber connected to the inlet side of said compressor, said shell having a dome, a mufiler on one side of said motor having a discharge chamber con- 7 8 nected to the outlet side of said compressor, an internal said bypassed gases passing around said dome and directly type electrical protector mounted in heat-conductive relaaffecting said internal protector. tion with said stator below said dome and on the side of said motor opposite said muffier and adapted to discnable References Cited y the Examine! said motor in response to excessive motor current or shell 5 UNITED STATES PATENTS temperature, and a normally closed valve connecting said 2 946 203 7/1960 Carver 230*17 discharge and suction chambers, said valve being adapted 3:080:103 3/1963 MAnister to open in response to the attainment of a predetermined amount of pressure differential between said chambers so I LAURENCE V, EFNER, Primary Examiner. as to bypass discharge gases to the suction chamber with 10 

1. IN COMBINATION, A REFRIGERANT COMPRESSOR, AN ELECTRIC MOTOR FOR DRIVING SAID COMPRESSOR, A SUPPLY CIRCUIT FOR SAID MOTOR, AN ELECTRICAL PROTECTOR IN SAID SUPPLY CIRCUIT AND ADAPTED TO OPEN SAID SUPPLY CIRCUIT IN RESPONSE TO EXCESSIVE HEAT OR TEMPERATURE, A SUCTION CHAMBER CONNECTED TO THE INLET SIDE OF SAID COMPRESSOR AND IN HEATCONDUCTIVE RELATION WITH SAID PROTECTOR, A DISCHARGE CHAMBER CONNECTED TO THE OUTLET SIDE OF SAID COMPRESSOR, AND A NORMALLY CLOSED VALVE CONNECTING SAID CHAMBER AND ADAPTED TO OPEN IN RESPONSE TO THE ATTAINMENT OF A PREDETERMINED PRESSURE DIFFERENTIAL BETWEEN SAID CHAMBERS TO PERMIT FLOW FROM SAID DISCHARGE TO SAID SUCTION CHAMBER, WHEREBY HEAT CARRIED BY THE DISCHARGE GASES PASSING THROUGH SAID VALVE WILL ACT UPON SAID PROTECTOR. 